The state of Texas is about to lose more than 150 years of accumulated clout in Congress.

Fully one-fourth of the state's 24-member House delegation - the nation's fifth largest - will be retiring this year. And among the retirees are four of the most senior men on Capitol Hill.

They will take with them two committee chairmanships and a subcommittee chairmanship, as well as a network of power relationships that over the years has helped make the delegation one of the Hill's best at advancing the interests of its state.

The four are:

George H. Mahon, who came to Congress in 1935 and is chairman of the Committee on Appropriations.

Olin E. (Tiger) Teague, 33 years in Congress and chairman of the Committee on Science and Technology.

W. R. (Bob) Poage, first elected in 1935 and chairman of the Agriculture Committee's subcommittee on livestock and grains.

Omar Burleson, 32 years in Congress and member of both the Budget and Ways and Means committee.

In addition, the delegation is also losing the eloquent and well-known Barbara Jordan, and Robert Krueger, who is leaving to run for the Senate.

There are ironies in the retirements: When Mahon came to Congress in the middle of the Depression, the issues of the day included a Social Security system, the Italian government, and war in Ethiopia: as he leaves, there are problems with Social Security, the Italian government and war in Ethiopia.

To a great extent, the Texas departures reflect the 29 other retirements from the House announced or expected at the end of the 95th Congress - health (Teague), ambition for other office (Krueger), age (Mahon), and personal reasons (Jordan).

But they also represent significant national changes.

They are among the last vestiges of the rural southern coalition that controlled Congress for so many years. "These Texans are southerners, too, and to have these go out, that attenuates considerably the seniority of the whole House," says David R. Mayhew, a professor of political science at Yale University.

In addition, "we've now reached the final shake-out of the power-houses of the '30s that moved into power and reached a pinnacle with Lyndon Johnson," says former Deputy Agriculture Secretary John C. White, a Texan who recently became Democratic national chairman.

Finally, there is in the retirements an element of response to the changes that have deprived many of the Hill's "old bulls" of the power they once wielded.

"There's a whole new system that I don't like," says Poage, who was bounced from the chairmanship of the Agriculture Committee three years ago in an assualt on the seniority system. "I don't have to put up with it."

In Texas, the retirements of so many of such power will cut deeply into the towering influence the state has wielded in the national legislature through more than a generation. It was an influence reflected in many ways: Sam Rayburn convening his board of education over bourbon and perhaps chili in the speaker's hideaway; Lyndon Johnson running the Senate; the bringing of the B-58 bomber contract to Forth Worth, the putting of NASA's manned space flight center in Houston, the placing of Rep. J.J. (Jake) Pickle (D-Tex.) on the committee on Science and Technology ahead of a more ranking Pennnian.

"It means a lot for that state," says Mayhew. "It's a very tightly knit unity, and they attend to the needs of the unit."

"Texans saw themselves as making a career of the House," says political scientist Barbara Sinclair, who once studied the delegation, "and they were willing to get along in any way that did not [go against their beliefs]. There was a feeling. 'We may vote differently, but we can work together.' This might be the period in which they're tested."

To be sure, the state has not been left impotent. There is, after all, Rep. Jim Wright, the majority leader from Ft. Worth, and Jack Brooks, chairman of government operations ("Jack Brooks," says Sinclair, "is no piker when it comes to knowing how to get things done.")

"There are other members of the delegation who are far from lacking in influence," says Wright, who cites veteran's affairs chairman Ray Roberts, and Pickle, now on Ways and Means, and E. (Kika) de la Garza, who will move to second on Agriculture after Poage's retirement.

But there is perhaps no one to replace George Mahon, chairman of the Appropriations Committee, chairman of its subcommittee on defense appropriations. "When something is authorized, it has to be funded," is the way Wright assessed that influence.

"I can recall 1961 when the President's budget request left out all money for manned bombers -" There followed a brief story on the legislative process, which ended with $530 million voted for B-58s built in Wright's district. Wright adds, with some stress, that whatever Texas has received from the federal government, "valid national purposes have been served," like those bombers, or Padre Island National Seashore or Big Thicket national forest.

Whoever is elected to succeed the six retiring Texans, there will be changes other than in influence. Mahon, Teague, Poage and Burlesoa were first elected in times when their districts were predominantly rural. Now, budding metropolises have sprung up, almost sure to give their successors a more urban orientation.

Republicans, too, hope that the six wide-open contests will increase their chances, particularly in districts where the incumbents were given their closest races ever in 1976.

Whatever happens, Wright is optimistic. "When it comes to something in the interest of the state, there is remarkable unity. I like to think that those who will replace them will be as prone to unity as those they replace."